Phosphosulfurized material and extreme pressure lubricant containing the same



3,097,170 Patented July 9, 1963 "ice No Drawing. Filed July 5, 1962, Ser. No. 207,807 3 Claims. (Cl. 25246.7)

This invention relates to additives for mineral oil com positions and more particularly to oil-soluble agents which impart improved pour point, extreme pressure or load- .carrying characteristics and anti-wear properties to the lubricant.

With the advent of higher compression internal combustion engines, much difiiculty has been experienced in formulating a suitable lubricating oil composition capable of operating under severe conditions to protect effectively metal surfaces which come in contact with the oil. It is well known that the high pressure occurring in certain types of gears and bearings may cause a film of lubricant to rupture with subsequent damage to the machinery. It has been shown that base lubricants such as mineral oil and/ or synthetic oil can be improved with regard to their protective effect on rubbing surfaces by the addition of certain substances so that excessive wear, scufling and seizure which normally follow a break in the film of lubricant can be prevented even under the most unfavorable pressure and speed conditions. Lubricants possessing this highly desirable property are called extreme pressure lubricants.

Certain classes of compounds can be used to improve specific properties of base lubricants. Thus, compounds containing sulfur, chlorine, phosphorus or lead or combinations of these elements may improve the extreme pressure properties of a lubricant. However, the simple presence of these elements does not guarantee extreme pressure properties and various compounds that do have these properties can vary considerably in their effectiveness. It is generally believed that the effectiveness of an extreme pressure additive is related to its ability to react with and form a protective coating on a bearing surface to be lubricated. -To be most effective, however, the additive must be present in sufficient concentration at the surfaces to form an adequate film. One method of realizing this surface concentration is the use of polar or other type molecules which have an affinity or attraction for surfaces. Thus, as opposed to the use of a non-polar molecule which will be present in more or less equal concentration throughout the bulk of the lubricant, a polar type mole cule will tend to give a greater concentration of additive at the metal surface where it is needed.

-In a similar manner a strongly polar material which is not an extreme pressure additive can interfere with the function of a less polar extreme pressure additive. Thus, a strongly polar non-extreme pressure molecule may be preferentially deposited from its admixture with an extreme pressure additive and prevent the extreme pressure additive from forming its protective extreme pressure film.

My invention is directed to a lubricating oil composition containing essentially a major amount of a mineral lubricating base oil and an oil-soluble tetraester of a complex acid and an unsaturated aliphatic alcohol, which ester has been phospho-suifiurized. This tetraester additive has been found to improve pour point, load-carrying and anti-wear properties of lubricating oils. Thus, the ester reaction product of a complex acid such as ethylene diamine tetraacetic acid, which contains sulfur and phophorus and several polar groupings in the same molecule, has been found to provide a lubricant additive having advantageous anti-wear and extreme pressure characteristics. The tetraester is formed from carboxylic acid groups preferably of lower aliphatic acids such as acetic, propionic, butyric, and the C and C aliphatic acids and an unsaturated aliphatic alcohol generally having about five carbon atoms or more. In general the acid has the molecular structure:

where R is a divalent hydrocarbon radical of say 1 to 5 carbon atoms and R is a diva-lent hydrocarbon radical, preferably aliphatic, of 2 to 6 carbon atoms. The preferred acid for my invention is ethylene diamine tetraacetic acid and has the following molecular structure:

The ethylene diamine tetraacetic acid used in forming the reaction products is an efficient chel-ating agent; that is, a chemical which complexes polyvalent metallic ions with amulti-ring structure that inactivates the metal. This property has been used in a variety of applications.

The unsaturated aliphatic alcohols of the present invention generally have about 4 to 22., preferably about 8 to 20, carbon atoms and include unsaturated cycloaliphatic alcohols such as cycloalkenols and less desirably aromatics having unsaturated acylic or cyclcal-iphatic substituents. These alcohols have an unsaturated or double bond between acylic or cycloal-iphatic carbon atoms with the alcohol hydroxyl group also being attached to the same acylic or cycloaliphatic carbon chain. The preferred alcohols are the unsaturated acylic aliphatic alcohols as, for example, trimethyl pentanol-2,2-ethyl hexanol-l, etc. It should be emphasized that saturated alcohols are unsuitable for use in the present invention since phosphosulfurization of the tetraester produced from the acids of the present invention and saturated alcohols results in a reaction product which is unstable in lubricating oils, effecting cloudy blends that eventually form voluminous precipitates.

-In making the ester the appropriate acid and methanol are mixed, and the solution is refluxed and heated for the necessary period of time to obtain esterification. The time of refluxing is related to the particular constituents employed and is not considered critical. The period of time will generally range from about 2 to 14 hours. After refluxing is completed excess alcohol is distilled off. Then a sufficient quantity of a low molecular weight alcohol such as iso-butanol along with a catalyst such as tetraocty-lene glycol titanate is added to facilitate transester-ifloation. 'I he constituents are heated for approximately 5 to 8 hours at a temperature of about to about C. The product thus obtained is added to a higher molecular weight unsaturated aliphatic alcohol and a solvent such as xylene, and a catalyst such as octylene glycol titanateis added to facilitate ester interchange. The reaction is now maintained at a temperature from about 140* to 160 C. for a period of from about 5 to 10 hours. The solvent is then removed by distillation.

The tetraester of the acid thus obtained is phosphosulfurized by the addition of phosphorus and sulfur compounds such as P 8 P 8 P 5 and the like. The subsequent heating and filtering completes the reaction and facilitates the recovery of the final product. The temperature for phosphosulfurizing can vary from about to 450 F. with the preferred temperature being about 250 to 300 F. Generally in preparing the additive I employ about 1 to 10% by weight of the phosphorus sulfur compound based on the unsaturated ester.

The mineral oil base stock used in the present invention'is of lubricating viscosity and can be for instanw a solvent extracted or solvent refined oil obtained in accordance with conventional methods of solvent refining lubricating oils. Generally, lubricating oils have viscosities from about 20 to 250 SUS at 210 F. The base oil may be derived from parafinic, naphthenic, asphaltic or mixed base crudes, and if desired, a blend of solvent-treated Mid-Continent neutrals and Mid-Continent bright stocks may be employed. A particularly suitable base oil used in the preparationof the compositions described hereinafter is a solvent treated Mid-Continent neutral having a viscosity index of about 95.

The amount of reaction product added to the lubricating oil is sufi'icient to impart extreme pressure and antiwear properties to said oil. Thus, the amount of ester added can vary in amount depending upon the particular characteristics of lubricating oil utilized. In general from about 0.1 percent of the phosphosulfurized reaction product by weight to about 10 percent of the final composition by weight is utilized in my lubricating oil composition with a preferred amount of from about 1 to 5%. Although my additivehas been described as the tetraester it may contain portions of less esterified materials such as diand tri-esters.

My composition can also contain other additives such as anti-oxidants, anti-foaming agents, etc.

The following examples, not to be construed as limiting, are ofiered to further illustrate the novel additive and lubricating oil composition of my present invention.

Example I '73 grams of ethylene diamine tetraacetic acid are added to 320 grams or methyl alcohol and refluxed with stirring for a period of about 3 hours. 10 grams of concentrated H01 is then added and the mixture is refluxed for about 8 hours and thenthe reaction product is recovered and the excess alcohol is distilled off. The light amber, viscous product i round to be insoluble in mineral oil, (ii-(2- ethylhexyD-sebacate, toluene and 2-ethylhexanol, but soluble in iso-butanol. 225 grams of iso-butanol and 1 gram or tetraoctylene glycol titanate are added to the above product to facilitate ester interchange. The reaction is maintained at approximately 130 C. for a period of about 6 hours. This is accomplished by gradually removing reflux as distillate during the above period. The product is analyzed to be 3.87% nitrogen. Next 255 grams of the tetrabutyl ester of ethylene diamine tetraacetic acid is added to 530 grams of an unsaturated alcohol known as M-akanol 8 (Makanol 8 is described as an alcohol resulting from the sodium reduction of soybean oil and consists of '12%- saturated and 88% unsaturated fatty alcohols having'an average molecular weight of about 265). Then 500 ml. of xylene solvent and 5 grams of tetra-octylene glycol titanate were added to' facilitate ester'interchange. The temperature is'then maintained at about 150 C. for about 8 hours. The solvent is then removed by vacuum distilaltion at a temperature of about 10 C. The'product thus formed can be called Product A.

Example 11 About 264 grams of Product A isadded to about 36 grams of sulfur and then reacted :tor about 24 hours at an approximate temperature of 320 F. The product Thus obtained is called Product B.

Example III About 410 grams of Product A is added to about 8 grams of P S and heat applied with constant stirring for a period of approximately one hour thus obtaining a temperature of about 250 F. The solution is then maintained at this temperature for approximately one hour and then the temperature is increased to approximately 300 F. for about 16 hours. The reaction mixture is then filtered to yield approximately 418 grams of a bright yellow viscous liquid analyzed as containing sulfur, 0.92%; phosphorus, 1.07%. This product is called Product C.

Example IV Shell 4-ball wear test Mean Hertz load SAE load test Falex load [test Timken L-20 test These tests have been ct'ully described in literature under the subject of anti-wear and extreme pressure testing. Thus, I will not attempt to go into any detail concerning the procedures of each. The possible exception to the above is the Timken L-20 test which is run using the Timken machine described in CRC L-18-545. The test block is continuously moved back and forth beneath the test cup in a direction paralleling the level arm for a distance 'for about 0.13 inch at an approximate rate of about 4 times per minute. Conditions for load, speed, time and temperature may 'be varied and are noted for each given test.

The following table reveals results and comparisons between similar tests on a'base oil, a conventional motor oil additive and my products. The base oil is a V1. solvent refined Mid-Continent neutral oil having a viscosity of about 33 SUS at -F. The rnotor oil additives included about 3 percent of a solution of 15 weight percent basic barium mahogany sulfonate in petroleum oil along with 1.8 percent of 50 percent zinc dithiophosphate diester in petroleum-oil. Products C and D were readily soluble in the base oil and each produced clear blends.

Blend N0 e 1 2 3 4 Base Oil, Wt. percent 100 95. 2 9

Motor Oil Additives 4. 8 8 98 Product 0 2. 0 Product D e 2.0 Shell t-Ball Wear Test, Scar Diam.,

mm. (7kg., 2hrs. llOC., 640 .p.m.) 0.687 0.247 0.290 O. 280 Mean Hertz Loa 13. 7 26. 9 33.8 40. 7 SAE at 300 r.p.m., lbs Fails at 67 121 132 Falex Breakdown, lbs Start of 1, 600 4, 500 3, 750 'Iimken L-20 Test, Total Wear, mg; Test 100 lbs. 200 F., 200 r.p.m., 16 hrs- 254 14.1 12. 5 lbs. 200 F., 200r.p.m., 16 hrs. 14. 3 Pour Point of Blend, "F 10 10 15 10 HO 0 (3-K RO O OH wherein R is a divalent hydrocarbon radical of 1 to 5 carbon atoms and R is a divalent hydrocarbon radical of 2 to 6 carbomatoms, said phosphosulfurized tetraester being the reaction product of said tetraester and about 1 to 10% by weight of a phosphosulfurizing phosphorus-sulfur compound.

2. A lubricating oil composition consisting essentially of a mineral lubricating base oil and about .1 to 10 percent of an oil-soluble phosphosulfurized tetraester of an unsaturated aliphatic alcohol of from 4 to 22 carbon atoms and carboxylic acid said acid having a molecular structure of the formula:

HOOC-R HOC-R R-OOOH wherein R is a divalent hydrocarbon radical of 1 to carbon atoms and R is a divalent hydrocarbon radical of 2 to 6 carbon atoms said phosphosulfurized tetraester being the reaction product of said tetraester and about 1 to by weight of a phosphosulfurizing phosphorus sulfur compound.

3. A lubricating oil composition consisting essentially R-COOH of a major portion of a mineral lubricating oil and about 0.1 to 10 percent of an oil-soluble phosphosulfurized tetraester of an unsaturated aliphatic alcohol of 8 to carbon atoms and ethylene diamine tetraacetic acid said phosphosulfurized tetraester being the reaction product of said tetraester and about 1 to 10% by weight of a phosphosulfurizing phosphorus-sulfur compound.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF AN MINERAL LUBRICATING BASE OIL AND A MINOR AMOUNT EFFECTIVE TO IMPROVE THE LOAD CARRYING PROPERTIES OF THE OIL OF AN OIL-SOLBULE PHOSPHOSFLURIDED TETRAESTER OF AN UNSATURATED ALIPHATIC ALCOHOL OF FROM 4 TO 22 CARBON ATOMS AND CARBOXYLIC ACID SAID ACID HAVING A MOLECULAR STRUCTURE OF THE FORMULA: 